class_docstr: Searches for structured entities, e.g. dates, using a duckling server.
docstr: Return url of the duckling service. Environment var will override.
docstr_tok: ["Return","url","of","the","duckling","service",".","Environment","var","will","override","."]
code: def _url(self) -> Optional[Text]:
      """Return url of the duckling service. Environment var will override."""
      if os.environ.get("RASA_DUCKLING_HTTP_URL"):
          return os.environ["RASA_DUCKLING_HTTP_URL"]
  
      return self.component_config.get("url")
  
imports: from __future__ import annotations
  import time
  import json
  import logging
  import os
  import requests
  from typing import Any, List, Optional, Text, Dict
  import rasa.utils.endpoints
  from rasa.engine.graph import GraphComponent, ExecutionContext
  from rasa.engine.recipes.default_recipe import DefaultV1Recipe
  from rasa.engine.storage.resource import Resource
  from rasa.engine.storage.storage import ModelStorage
  from rasa.shared.constants import DOCS_URL_COMPONENTS
  from rasa.shared.nlu.constants import ENTITIES, TEXT
  from rasa.nlu.extractors.extractor import EntityExtractorMixin
  from rasa.shared.nlu.training_data.message import Message
  import rasa.shared.utils.io
label_desc: Use image node_id 4 for calling the DucklingEntityExtractor obj's underlying member method code with example usage: obj._url() and returns: self, os